Story: Gold and gold mining

Page 7 – Methods of mining

When a miner found an area of payable ground he pegged out
a square claim. The size of claims varied among goldfields,
but were usually 24 feet square (53.5 square metres). Miners
often teamed up with mates to share claims and workings.

Shovel, pan and cradle

Gold mining was rough, physical work. Where alluvial gold
was very rich, it could be obtained with a shovel and pan.
However, pans were used mainly for prospecting. Simple
machines known as cradles (often made from wooden liquor
boxes) were rocked back and forth – the heavier gold
collecting on matting on the cradle base.

Sluice boxes

Riffle or sluice boxes were the main methods of recovering
gold. Nicknamed Long Toms, these were long, terraced wooden
boxes, over which gold-bearing gravel was washed. Each step
of the box had a lip that trapped the heavier gold and
allowed the lighter materials to wash away. Eventually the
heavy gravel and gold caught in the terraces was washed up in
a pan.

These methods all relied on water, without which
recovering gold was impossible. At each of New Zealand’s
goldfield’s there were small dams and water races – channels
that cut across contours, bringing water from creeks to areas
where gold was worked.

Sluicing

Sluicing was a method where water was piped into
successively narrower pipes leading to hoses (with nozzles
called monitors), which sprayed jets of water strong enough
to kill a person. The jets were aimed at gravel faces and
helped to wash gold-bearing gravels down through sluice
boxes. In places like Bannockburn and St Bathans in Central
Otago distinctive gravel pillars are a legacy of these giant
water guns.

Hydraulic engineering

Hydraulic elevators were used to reach leads of alluvial
gold that were covered by gravel. Most elevators worked like
giant vacuum cleaners, sucking a slurry of gravel and water
up from beneath large gravel terraces.

Engineering was also used to expose river beds. The
Oxenbridge tunnel on the Shotover River and the dam gates
across the source of the Kawarau River draining Lake Wakatipu
at Frankton are the two most famous examples. Both were
spectacular failures – little gold was found in the exposed
bed of the Shotover once water was diverted through the
tunnel. And when the Kawarau dam gates were closed they had
little effect on water levels downstream.

Hard-rock mining

Hard-rock mines followed quartz veins, which contained
gold. Underground mining was very expensive as tunnels had to
be blasted and the roofs supported. Mines such as those at
Waihī on Coromandel Peninsula and Waiuta on the West Coast
followed reefs until they became too deep or low grade to be
mined economically. The recovered quartz was crushed by
stamper batteries, and cyanide was used to reclaim the
gold.